Is there a way to move from one message to the next without opening each individual message? I found the "Move to next unread" and "Move to previous unread" but is there a way to move to any message, even the already read ones? Thanks for pointing me in the right direction.

I just use the Message Autoview mode (available from the View menu) so I see both the list of messages and the currently highlighted message. That way, I don't have to actually open messages to read them, and when I want to read another message, I just click on it in the list.

If you don't want that, you can also 'open' messages and still see the list -- use 'View | Show Message List' in your open message.